On Kinematics of Lower Mobility Planar Parallel Continuum Robots

Lower Mobility Manipulators have end-effectors that exhibit a type of motion constrained in some degree. This constraint is due to some combination of passive kinematic pairs and rigid elements. Translational mechanisms are the most typical examples on this mechanism sub-type. In the case of using flexible elements, such as in Parallel Continuum Manipulators, the constraint is no longer rigid, but a difficulty exists to undergo certain motions depending on some compliance. The mobility analysis is no longer solely a geometric issue but is strongly dependent on the force distribution on the mechanism. A direct transformation of classical lower mobility rigid-body parallel mechanisms into Parallel Continuum mechanisms may produce some results that are unexpected. In this paper, by way of a planar example, some interesting issues on obtaining parallel continuum robots with lower mobility type of motions are exposed.